1. Field of the Invention
The present invention relates to a semiconductor redundancy system having high reliability and, more particularly, to an on-chip redundancy high-reliable system using function blocks such as microprocessors or hard logic circuits provided redundantly in semiconductor chips.
2. Description of the Related Art
In the technical fields requiring systems such as aerospace systems, railroad systems, and vehicles of high safety, conventionally, higher reliability of a system is widely achieved by redundantly disposing a spare system as a backup. In particular, the integration degree of a semiconductor in a semiconductor integrated circuit is increasing in recent years. A function block circuit of a system level can be mounted on a semiconductor chip by a system on-chip method. For example, as disclosed in Japanese Unexamined Patent Application Publication No. H06-161798, a system redundantly provided with a plurality of function blocks can be realized in a single semiconductor chip. A method of constructing a redundant system in a semiconductor chip is an extremely excellent technique realizing reduction in size and weight of a built-in system, shortening signal delay time in a high-performance system, and improvement in performance.
In the conventional techniques, a physical damage such as breaking or crack occurs in a semiconductor chip by a heat cycle applied to the semiconductor chip under severe heat environment of, for example, −40 degrees Celsius to 150 degrees. It is therefore indispensable to consider a countermeasure for a failure exerting influence on an entire semiconductor chip. In a conventional method of assuring a normal state by comparing outputs of systems redundantly provided, since a comparator measure for detecting a failure is mounted in the semiconductor chip in which the redundant systems are also provided, the operation in the case where the influence of a failure is exerted on the comparator measure cannot be assured. In the case where a processor module and a comparator are formed in different chips like in the patent publication, the conventional technique cannot achieve high-speed process which is presently being demanded.
An object of the present invention is to improve reliability of an on-chip redundancy system mounted on a semiconductor chip by preventing influence of a failure from being exerted on an entire semiconductor chip.